Atoms For Dummies

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What is Matter?

Matter is what the Universe is made of.

What is an atom? Atoms are the basic building blocks of everything. Each atom is made of subatomic particles. These particles are protons, neutrons, and electrons. Protons and neutrons are in the Nucleus of an atom, while the electron orbits around the nucleus. How do we know the size of an atom? The size is estimated by describing its radius. This is done by measuring the distance between two nuclei in the solid state and dividing by two. These kind of measurements can be done with X-ray diffraction.

What is an element? An element is when all particles are alike, or a pure substance. Elements are the simplest pure substance. An atom, therefore, is the smallest particle of an element that has the properties of that element. So if you have an Oxygen atom, it has the same exact properties as another Oxygen atom.

What is the nucleus? The nucleus is the core of an atom, containing roughly 99.9% of the mass of the atom. While the nucleus contains most of the mass, it is very small. An comparison might be to think of a bee in the center of a football stadium.

What is a nucleon? Nucleons are the subatomic particles found in the nucleus. The particles make the nucleus spin. Their rates of spin are based on certain energy levels called its energy spectrum. If an atom is not spinning, its in its ground state, while if its spinning its in the excited state. The nucleons are arranged in orbits, based on the amount of activity they possess.

What is a Proton? Protons are positively charged. All protons are identical, regardless of the element. The mass of the typical proton is roughly 1amu. 1 amu is often defined as 1/12 the mass of a carbon-12 atom. Protons are often used to figure out the atomic number.

What is a Neutron? Neutrons are electrically neutral. All neutrons are identical, and have more mass than do protons, but they still consider the mass to be 1amu.

Atomic Number: What determines the atomic number? The number of protons in a nucleus. Why? This determines what element the atom belongs to. The atomic number identifies the element.

Isotope: Even though the atomic number of an element will never change, the number of neutrons may change. Atoms of the same element that have the same number of protons but different numbers of neutrons are called isotopes.

Atomic Mass: Is the average of all the isotopes of that element as they occur in nature. This is why it is not always a whole number.

Electrons: particles that are 1/2000 the mass of a proton or neutron. Electrons have a negative charge and a mass of 1/1836amu. In an uncharged atom the number of electrons equals the number of protons, so it is said that this atom is neutral. Electrons whirl around the nucleus at billions of times per second.

Electron cloud: Is a space in which electrons are likely to be found. A comparison can be found in comparing bees to a beehive. Each electron is locked into a certain area of the electron cloud. The location of an electron depends on how much energy it has. Electrons are arranged in energy levels. Electrons with the lowest energy are found closest to the nucleus, while the those with the highest energy are found farthest from the nucleus.

Valence number: What on earth is a valence??? Valence determines how many electrons an element will gain, lose or share. For example. An element with a valence number of 4 could gain, lose or share 4 of its electrons. An element with a valence number of 0 could gain, lose or share none of its electrons. Why is this? Its outermost energy level is full, and the element is said to be inert.

How do we know this?: If we arrange the elements by atomic mass and valence numbers, we see a pattern emerge…… 1234321. If we keep going higher and higher in atomic numbers, we start to see that not only are they arranged in rows but the pattern repeats itself to the point of making columns as well. All the elements in a column have the same valence!

Orbital: The energy levels that the electrons are organized in. These come in various shapes around the nucleus.

Periodic Law: Elements are arranged by atomic number, and by doing this elements with similar physical and chemical properties fall into place! To put this into scientific terms for all the science minded, Periodic Law states that the physical and chemical properties of the elements are periodic functions of their atomic numbers.

What is the Periodic Table? The Periodic Table is a classification system. Based on its position in the Periodic Table, you can predict its physical and chemical properties.

Columns of the Periodic Table: There are 18 main columns of elements in the Periodic Table. These are called groups or families. Elements within the same group or family have similar but not identical properties. For example lithium 3, sodium 11, and Potassium 19 are members of family 1. They are all highly reactive, and thus can easily combine with other elements to form compounds.

Rows of the Periodic Table: Each horizontal row is called a period. Unlike elements in a family, elements in a period are not alike in properties. What you do notice is that the first element in each period is an extremely active solid, while the last element is an inactive gas. There are seven periods of elements. The two rows that have been separated out of the main table are rare-earth elements.

Metals: Most of the elements on the periodic table are metals. The 88 elements to the left of the zigzag line are metals. All metals have several physical properties. One, is that they have a luster, or that they are shiny. Also, metals are able to conduct electricity. Metals are usually high in density, and metals have high melting points. Most metals are ductile, or they can be drawn out to wires, and most metals are malleable, which means they can be hammered into sheets.

Chemical properties of metals: These will depend on the electron arrangement in the outer energy shell. Most metals tend to lose their outermost electrons when they combine chemically. Because metals lose their electrons, they tend to react with water or the atmosphere, this reaction is called corrosion.

Nonmetals: Elements that are nonmetals are located to the right of the zigzag line in the periodic table. Fewer elements are classified as nonmetals. The properties of nonmetals tend to be the opposite of metals. For example, nonmetals have no luster and are dull. Nonmetals do not conduct heat or electricity and are brittle and break easily. Nonmetals are ductile or malleable. They also have lower melting points. Nonmetals are also not as easy to recognize as a group as are metals.

Chemical Properties of Nonmetals: Most nonmetals have 5,6,7,8 electrons in their outer most energy level. Nonmetals tend to gain electrons when they combine chemically. The atoms with 8 valence electrons have a complete outermost energy level. This makes them nonreactive, and much more difficult to form compounds.

Metalloids: The elements that are along the zigzag line are called metalloids. They have properties of both metals and nonmetals. They conduct heat and electricity better than non metals, and are ductile and malleable.

Periodic Table Families:

Family 1: The Alkali. These atoms have a single valence electron in their outermost energy level. These metals are soft, silver-white, and can be cut with a knife. They react readily with other substances. They are usually not found uncombined in nature. These elements react violently when exposed to water or oxygen so are kept in oil or kerosene to keep them from exploding. These elements form some of the most used substances such as salt and baking soda.

Family 2: The alkaline earth metals. These are also never found in nature as uncombined elements. They are usually combined. These elements have 2 valence electrons which they lose easily when they combine with other atoms.

Transition metals: Between families 2 and 13 are the transition metals. These families seem to not fit into any other family. These are metals that you are most familiar, such as copper, tin, zinc, iron, etc… Transition metals are good for conducting heat and electricity. They are also brightly colored, so they are often used to color paints. Most transition elements have 1 or 2 valence electrons, that they lose one or two of. Transition metals can also lose an electron from the second to outermost energy level.

Family 13: The Boron family. All elements in family 13 have 3 valence electrons. Some examples of family 13 are boron (metalloid), and Aluminum.

Family 14: The Carbon family. These elements all have 4 valence electrons. Carbon is a nonmetal, while silicon and germanium are metalloids, and tin and lead are metals. Family 14 elements, due to their 4 valence electrons form roughly 5million compounds.

Family 15: The Nitrogen family. Nitrogen makes up 78% of the air around us. The elements in this family have 5 valence electrons. They tend to share their electrons.

Family 16: The Oxygen family. These elements have 6 valence electrons. Most of the elements in this family share electrons when forming compounds.

Family 17: The Halogens. Halogens have 7 valence electrons which is why they are the most active nonmetals. All they need is just one electron to fill their outer shell. They are very reactive and are therefore not found in nature. They tend to react with the alkali metals quite easily. One common example of this would be NaCl, or sodium chloride, or table salt. When halogens react with metals they form salts.

Family 18: The Noble Gases. All the gases in this family are unreactive. They are also referred to as inert gases. Why are they so inert? They do not need to fill their outer energy level so they don’t need to combine with other elements. The only noble gas to not have 8 valence electrons would be helium, that only has 2.

Rare Earth Elements: These elements have properties that are similar to one another. Some examples are:

Lanthanoid series: soft malleable metals that have a high luster and conductivity. These are used to make alloys and high quality glass.

Actinoid series: All the actinoids are radioactive. This means that changes in the nucleus of radioactive atoms cause particles and energy to be given off. Most are synthetic, or made in the lab. The most famous actinoid is uranium.